When the Vatican last July announced Pope Francis’ plans to canonize both Popes John XXIII and John Paul II, there was speculation that the dual event might take place before the end of 2013. Winter weather concerns and time constraints, however, dictated a different plan. In September, a final date was announced: that of this Sunday, April 27 — the Second Sunday of the Easter season, also known as Divine Mercy Sunday.

As it turns out, no more fitting date could have been chosen to confer sainthood on these two holy men. Sts. John XXIII and John Paul II could very well be called “the mercy popes,” as their pontificates embodied this theme in very particular ways. John XXIII, known so well for calling the Second Vatican Council, coined the phrase “the medicine of mercy” in Gaudet Mater Ecclisea (“Mother Church Rejoices”), his opening speech to the council. In it, he said: “The Church has always opposed ... errors (of truth). Frequently she has condemned them with the greatest severity. Nowadays, however, the spouse of Christ prefers to make use of the medicine of mercy rather than that of severity. She considers that she meets the needs of the present day by demonstrating the validity of her teaching rather than by condemnations.

As the Church welcomes two new saints, we have the opportunity to reflect on what it means to be a merciful people.

“That being so,” he added, “the Catholic Church, raising the torch of religious truth by means of this ecumenical council, desires to show herself to be the loving mother of all, benign, patient, full of mercy and goodness toward the children separated from her.” These words, spoken at a tumultuous time for the Church and the world, sought to reconcile Catholics to the Faith as children would be reconciled to an estranged mother. Fifty years later, they are just as relevant and just as poignant.

John XXIII’s theme of mercy was only expanded on by his successor, Pope John Paul II, who penned Dives in Misericordia (“Rich in Mercy”) as one of his first encyclicals. He also canonized St. Faustina Kowalska who, in the 1930s, received a message of mercy from the Lord that she was told to spread throughout the world, and he declared the Second Sunday of Easter to be Divine Mercy Sunday in the universal Church.

But perhaps his most dramatic emphasis of mercy took place in 1983 when John Paul II met face to face with his would-be assassin, Mehmet Ali Agca, in “a moment of reconciliation that captured the world’s attention,” as Baltimore Archbishop William E. Lori phrased it in a speech earlier this month. In that meeting, John Paul forgave Agca for shooting him four times, and, in doing so, showed the world what it means to be truly merciful.

Today, Pope Francis continues to actively live the call of his predecessors for mercy, a common link that bonds the three men together. Because humans are naturally judgmental, “it is not always easy to understand this attitude of mercy,” Pope Francis said in a daily homily last month.

But he prescribed for us a remedy. “To be merciful,” he said, “two attitudes are needed.” The first is knowledge of oneself — that we are sinners. And the second is a large heart. A “small” and “egotistical heart is incapable of mercy,” he said. “Make the heart grow,” and peace will follow.

This is what John XXIII knew when he spoke the phrase “medicine of mercy.” And it’s what John Paul II knew when he sat in a prison cell with his attacker. And because of these three men, it’s what we celebrate on this Divine Mercy Sunday when the Church welcomes two new saints.